Problem: $ B = \left[\begin{array}{rrr}1 & 2 & 2 \\ 0 & 1 & 2 \\ 2 & 2 & 1\end{array}\right]$ What is $ B^{-1}$ ?
$ = \left[\begin{array}{rrr}-3 & 2 & 2 \\ 4 & -3 & -2 \\ -2 & 2 & 1\end{array}\right]$